This invention relates to a braided suture of improved construction featuring a cabled core component.
Sutures intended for the repair of body tissues must meet certain requirements: they must be substantially non-toxic, capable of being readily sterilized, they must have good tensile strength and have acceptable knot-tying and knot-holding characteristics and if the sutures are of the absorbable or biodegradable variety, the absorption or biodegradation of the suture must be closely controlled.
Sutures have been constructed from a wide variety of materials including surgical gut, silk, cotton, a polyolefin such as polypropylene, polyamide, polyglycolic acid, polyesters such as polyethylene terephthalate and glycolide-lactide copolymer, etc. Although the optimum structure of a suture is that of a monofilament, since certain materials of construction would provide a stiff monofilament suture lacking acceptable knot-tying and knot-holding properties, sutures manufactured from such materials are preferably provided as braided structures. Thus, for example, sutures manufactured from silk, polyamide, polyester and bioabsorbable glycolide-lactide are braided to provide optimum knot-tying and knot-holding properties.
Currently available braided suture products are acceptable in terms of their knot-tying and knot-holding properties. However, as removed from the package, they tend to be stiff and wiry and retain a "set" or "memory" such that at the time of use, it is usually necessary for the surgeon or assistant personnel to flex and stretch the suture to make it more readily handleable. Furthermore, the surfaces of known sutures are perceptibly rough. Thus, if one passes one's hand or fingers along the braid, surface irregularities will be readily detected. The result of this rough surface is that the suture will exhibit drag or chatter as it is drawn through tissue, characteristics which militate against smooth, neat, accurately placed wound approximation so necessary to excellence in surgical practice.
By way of overcoming the foregoing disadvantages which characterize commercially available braided sutures, U.S. Pat. No. 5,019,093 describes a braided suture of improved construction possessing a significantly greater number of sheath yarns for a given overall denier, the sheath yarns being fabricated from individual filaments of finer denier than filaments which are typical of known types of braided suture, the resulting improved suture exhibiting perceptibly improved flexibility and handling and reduced chatter and drag compared with braided sutures of known construction.
In all but the smallest size, the sutures of U.S. Pat. No. 5,019,093 can optionally be constructed around a filamentous core, a particularly advantageous feature in sutures of heavier denier. In some of these core-containing suture constructions, the larger number of sheath yarns in the braid may require a larger diameter core relative to that of a core of a similar braided suture constructed from fewer sheath yarns. However, a difficulty has been observed during the normal processing and handling of sutures possessing a somewhat larger core, namely, the core has a tendency in some cases to work through the surface sheath yarns. This "core popping" tendency can be diminished or eliminated by increasing the braid angle (the angle at which sheath yarns cross over each other in the braid). However, this solution to the problem of core popping can only come at the expense of surface smoothness of the suture since such smoothness decreases as the braid angle increases.